1. Field of the Invention
This invention relates to valve apparatus providing easy and rapid means for replacing the valve packing, and particularly to valve apparatus having a packing container, such as a stuffing box or packing cartridge, that is easily and rapidly removed from, and replaced in, the valve assembly, especially while the valve assembly remains in service and while the valve stem is disengaged from the packing container.
2. Description of the Prior Art
In the maintenance of valves, removal and replacement of packing materials from around the valve stem in the valve bonnet previously has been a difficult, time consuming and expensive task. Because the valve packing becomes compressed, hardened, congealed and brittle in use, removal of the packing generally required removal from service and disassembly of the valve apparatus, which is expensive and time consuming. In addition, removal of the packing material itself generally required the use of sharp instruments such as hooks, picks, corkscrews, screwdrivers, scrapers, wire brushes and like implements that are likely to damage the highly ground or polished valve stem and interior surfaces of the stuffing box. Damage to those surfaces results in a failure rate of valve packing and intolerable fluid leaks arising from the loss of the static seal between the packing and the stem or between the packing and the interior surfaces of the valve bonnet or other structural elements. Such damage often required replacement of the stem or entire valve assembly.
Various types of valve apparatus have been suggested for packing removal. U.S. Pat. No. 4,394,872 describes such a device having an annular drive bushing mounted in the valve bonnet chamber subjacent the bottom of the packing material. A stem collar is carried on the valve stem. When the packing is to be removed, the valve is removed from service, and the packing gland is disconnected and fastened to the valve yoke. The valve stem is then rotated on its threaded portion through a bushing in the valve yoke and moved upwardly to bring the stem collar into contact with the drive bushing and thereby displace the packing materials from the packing chamber of the valve bonnet.
U.S. Pat. No. 4,394,872 also describes a valve assembly for packing removal from a back seat valve. When removing the packing material from that apparatus, the valve is set in the fully open condition on the back seat. The packing gland is removed and a wire cage or other protective device, is mounted on the valve assembly surrounding the top portion of that assembly. The valve body contains a fluid expansion chamber formed below the valve bonnet. A fluid is forcibly injected into the fluid expansion chamber to displace the drive bushing and packing materials upwardly from the packing chamber in the valve bonnet.
U.S. Pat. No. 2,809,059 describes a valve having an annular abutment element mounted in the bonnet chamber adjacent the bottom of the packing material. The abutment element has a transverse internally threaded bore hole through the side of the abutment element which must be aligned with a bore hole in the valve stem and with a threaded bore hole through the side wall of the bonnet. During conventional use of the valve, a threaded Allen screw is positioned through the bore hole in the bonnet wall and partially through the bore hole through the abutment element to lock the abutment element in place and prevent its movement when the valve stem is rotated. When it is desired to remove the packing, the bore hole in the stem must be aligned with the bore hole through the abutment element and the Allen screw.must be inserted through the abutment element bore hole into the bore hole in the stem and beyond the interior surface of the valve bonnet chamber. The difficulty and disadvantage with that apparatus arises from the difficulty involved in achieving proper alignment of the bore holes between the valve stem and the abutment element and between the abutment element and the valve bonnet, in particular in view of the necessity of accounting for the vertical displacement of the valve stem inparted by the pitch of the threds on the valve stem upon its rotation. The operation becomes even more difficult as the valve seating surfaces wear, or remachining is performed, and the vertical positions of valve stem elements change with valve use. In any event, the packing material can not be removed or replaced while the valve is in service.
U.S. Pat. No. 3,237,917 describes a valve assembly in which the packing material is contained in a packing chamber of the valve bonnet and is supported by an intermediate bushing which rests on a lower bushing. The lower end of the valve stem has a cylindrical shoulder which could engage the lower bushing if the valve stem could be raised a sufficient distance. That operation is not possible with the structure shown in that patent because upward motion of the valve stem is restricted by several elements of structure. The packing gland is locked in threaded engagement with the upper end of the valve body to permit independent rotation of the upper gland. If the stem were rotated upwardly with the packing gland locked in place, the bushing and the packing material could not be displaced. On the other hand, removal of the packing gland introduces several problems. The packing gland can not be unscrewed from the upper portion of the valve body until after the valve stem handle and the bonnet are separately removed and the gland lock nut is loosened. In that condition, the packing gland can not be rotated outwardly simultaneously with the threaded stem because the compressed and hardened packing material will bind the stem and retain it within the valve body while the packing gland is rotated upwardly off the stem. If the packing gland is totally removed, the threaded stem will ride freely in the upper portion of the valve body and will not move upwardly upon rotation of the stem because of the loss of the stem's threaded connection to the packing gland which has been removed. With the packing gland removed, if the stem is forcibly jerked from the valve body to remove the packing, there is substantial danger of damaging the interior surfaces of the upper valve body and bonnet and the stem threads. In addition, that apparatus does not permit removal and replacement of the packing material while the valve is in service.
U.S. Pat. No. 3,157,381 describes apparatus having a chamber in the valve bonnet in which an annular resilient collar is mounted under the packing gland and a rigid annular carrier is mounted under the resilient collar. A sealing element is attached to the bottom portion of the rigid carrier in direct contact with the top surface of the valve closure member. That apparatus does not provide a container means for the sealing elements that is separate from, and readily removable from, the chamber surfaces in the valve bonnet. Hardening in use of the collar and sealing element would render difficult the displacement of those elements from the surfaces of the valve stem and the bonnet, especially because that apparatus provides no independent means to displace the collar and sealing element from the bonnet chamber without damaging the surfaces of the bonnet and the valve stem. In addition, that apparatus does not permit removal and replacement of the sealing elements while the valve is in service.
There remains a need for valve apparatus providing a container means for the valve packing elements which is physically separate from, and easily and rapidly removable from, the valve bonnet and other valve structural elements. There remains a further need for such a valve apparatus which permits easy and rapid removal and replacement of the valve packing elements while the valve remains in service.